1. Field of the Invention
This invention relates to a method of unilateral electroplating of a moving metal strip in which the strip as the cathode is in contact with an electrically conductive peripheral surface of a rotating roller and an anode concentric with the roller over a part of its circumference is located at a distance from the strip so as to form a slot into which electrolyte is supplied. The invention also relates to apparatus for carrying out the method.
2. Description of the Prior Art
Cells for electroplating continuous moving metal strip have been classified into three types, horizontal, vertical and radial. The present invention relates to the radial type. In the horizontal and vertical types, the strip passes without contact between a pair of spaced electrodes. Disadvantages are that the strip must be tensioned to hold it in the desired path through the cell and that the current must be fed along the strip which, especially with thin strip, creates resistance losses. These disadvantages are avoided by the radial type of cell where current is fed into the strip directly from the roller which it contacts in the cell, and tension needs to be applied only to hold the strip against the roller which accurately locates the strip. Only unilateral coating of the strip is possible, but two such cells can be arranged in series in the direction of strip movement. The strip width is, for example, l.5 m.
U.S. Pat. Nos. 3,900,383 and 3,483,113 show examples of radial type cells. In the apparatus of U.S. Pat. No. 3,900,383, the roller is half-immersed in a bath of electrolyte. In that of U.S. Pat. No. 3,483,113, FIG. 20, the anode extends around 270.degree. of the horizontal-axis roller and electrolyte is fed in opposite the lowest part of the roller so as to pass through the slot between anode and strip in two flows, one in the same direction as the strip movement and the other in the opposite direction to the strip movement.